Download a novel integrated power quality controller for microgrid

A NOVEL INTEGRATED POWER QUALITY CONTROLLER FOR MICROGRID
ABSTRACT:
A novel variable reactor based on magnetic flux control is proposed in this paper. The
system configuration of the novel variable reactor is presented, while its operational principle
and dynamic performance are analyzed. Based on the developed variable reactor, a novel
integrated power quality controller (IPQC) suitable for microgrid is proposed, which can cater
for the peculiar requirements of microgrid power quality, such as the harmonic high penetration,
frequent voltage fluctuation and over current phenomenon, and bidirectional power flow and
small capacity. For the fundamental, the equivalent impedance of the primary winding is a
variable reactor or capacitor. For the nth-order harmonic, the equivalent impedance is very high
impedance and acts as a “harmonic isolator.” The system control strategy is also analyzed in
detail. A set of three-phase IPQC has been constructed. The experimental test results verify the
validity of the novel variable reactor and the IPQC.
INTRODUCTION:
Distributed power generation has been emerged as a promising option to meet the growing
customer needs for electric power with an emphasis on reliability and environmentally friendly
renewable energy.
In this context, in order to maximize the operational efficiency of the distributed energy
resources (DERs) and take full advantage of distributed power generation, as an effective means
of integrating DERs into the traditional power grid, microgrid is presented, which can enhance
the local customer power supply reliability and system performance, reduce the impact on large
power grid, and minimize the system losses. Microgrid has good environmental and economical
benefits and has attracted more and more attentions of power researchers.
However, the power quality problem of microgrid is much more serious than that of the
traditional grid because of the intermittency and randomness of DERs, the high penetration
between conventional grid and microgrid, the diversity of DERs, load, energy conversion unit,
storage, and operating state. Microgrid power quality has the following unique features
compared with the conventional power grid
So far, relevant research studies on microgrid power quality con trollers can be sorted into two
types: unifunctional controllers and multifunctional controllers. Unifunctional power quality
controllers aim at a specific power quality issue in microgrid. Harmonic mitigation is mainly
investigated in .
Power flow control of microgrid is mostly analyzed . Voltage fluctuation is primarily concerned
in . The overvoltage and over current issue is the main concern. Multifunctional power quality
controllers generally combine the power quality controller with the grid interfacing converter
through special control scheme or topology .
However, these multifunctional power quality controllers do not take into account all of the
aforementioned features of microgrid. To date, there is less research on integrated power quality
controller (IPQC) particularly suitable for microgrid with the aforementioned features. In
addition, the microgrid capacity is comparatively small, and it is not cost effective to install
various types of power quality controller.
EXISTING SYSTEM:
This method employs an integrator with reset as its core component to control the pulse width of
an ac–dc converter so that its current draw is precisely opposite to the reactive and harmonic
current draw of the nonlinear loads. In contrast to all previously proposed methods, there is no
need to generate a current reference for the control of the converter current, thus no need to sense
the ac line voltage, the APF current, and the nonlinear load current.
Only one current sensor and one voltage sensor (resister divider) are used to sense the ac main
current and the voltage across the dc capacitor. The control method features constant switching
frequency operation, minimum reactive and harmonic current generation, and simple analog
circuitry. It provides a low cost and high performance solution for power quality control. Steadystate and dynamic analysis is performed that leads to the remedy of the dc offset related to peak
current sensing and extension of the stability region.
PROPOSED SYSTEM:
The novel IPQC can be installed in series and parallel in microgrid or point of common
coupling (PCC). For simplicity, the IPQC is installed in PCC. The three-phase detailed system
configuration of the IPQC with transformer and inverter. Us and Ls represent the source voltage
and impedance of conventional power supply, respectively. The passive filters, which have the
function of absorbing the harmonics, are shunted in both sides. The primary winding of a
transformer is inserted in series between the conventional power utility and the microgrid,
whereas the secondary winding is connected with a voltage-source PWM converter. Ud is the
voltage of the dc side of the inverter. The microgrid contains a harmonic load, a photovoltaic cell
system, a battery storage system, and a normal load.
ADVANTAGES:

Limiting the fault current.

Compensating the voltage fluctuation
BLOCK DIAGRAM:
Passive
filters
Load
Non linear
Load
Input DC
supply
Voltage
source
inverter
Filter
Voltage
source
inverter
Input source 1
12 V DC
3 phase driver circuit
Filter
5 V DC
BUFFER
circuit
Voltage
source
inverter
Input source 2
PIC controller
circuit
TOOLS AND SOFTWARE USED:

MPLAB – microcontroller programming.

ORCAD – circuit layout.

MATLAB/Simulink – Simulation
CONCLUSION:
This paper has presented a novel variable reactor based on the magnetic flux control. A
transformer with air gap is selected, and the primary winding current of the transformer is
detected. A voltage-sourced inverter is applied to follow the primary current to produce another
current, which is injected to the secondary. When the injected current is adjusted, the equivalent
impedance of the primary winding of the transformer will change continuously. The variable
reactor features hardly producing harmonics, simple control scenario, and with consecutive
adjustable impedance. The ramp comparison current control with PI controller, which is suitable
for DSP microcontroller, is chosen as control current. The optimum PI controller parameters
choosing criteria are given in this paper. When the injected current varies suddenly, the novel
variable reactor has excellent dynamic characteristic
REFERENCES:
[1] B. Lasse
ter, “Microgrids [distributed power generation],” in Proc. IEEE Power Eng. Soc. Winter Meet.,
2001, vol. 1, pp. 146–149.
[2] C. Marnay, F. J. Robio, and A. S. Siddiqui, “Shape of the microgrid,” in Proc. IEEE Power
Eng. Soc. Winter Meet., 2001, vol. 1, pp. 150–153.
[3] R. H. Lasseter et al., Integration of Distributed Energy Resources: The CERTS Microgrid
Concept. Berkeley, CA, USA: Consortium for Electric Reliability Technology Solutions, 2002.